Add standalone Analog Triggers add-on for continuous L2/R2 input

[pekado46]

Problem / Motivation:
L2/R2 mapped to potentiometers (using Direct / No Mux) were being reported as digital 0/1 inputs—even when set to 'Hall-Effect Trigger'—making it impossible to get true analog trigger responses.

Solution:
Added a standalone add-on instead of modifying the existing 'Analog' module. This avoids breaking shared code used by standard analog stick setups and accounts for trigger/pedal mechanics (which rest at an endpoint rather than centering like a joystick, requiring custom reading logic without center-calibration folding).

Testing:
Tested on RP2040 hardware controlling a steering wheel setup with dual potentiometer pedals. Confirmed smooth, gradual analog values in both Steam input settings and hardwaretester.com.

Implementation Details:
Follows the exact structure and pattern of existing lightweight add-ons (such as DRV8833 Rumble) to maintain codebase consistency.